Preamble: referenced user accounts

In subsequent sections, we will refer to a number of different accounts, as
follows:

Linux user accounts:

The user Linux account is the account that you use to log onto the
Linux system as a regular user.

The root Linux account is an account that has system administrator
privileges. On Debian and Fedora you can switch to this account from
your user account by issuing the su - command and entering the
password for the root account when prompted. On Ubuntu you can switch
to this account from your user account using the sudo su - command
and entering the password for your user account when prompted.

The opensrf Linux account is an account that you create when installing
OpenSRF. You can switch to this account from the root account by
issuing the su - opensrf command.

The postgres Linux account is created automatically when you install
the PostgreSQL database server. You can switch to this account from the
root account by issuing the su - postgres command.

PostgreSQL user accounts:

The evergreen PostgreSQL account is a superuser account that you will
create to connect to the PostgreSQL database server.

Evergreen administrator account:

The egadmin Evergreen account is an administrator account for
Evergreen that you will use to test connectivity and configure your
Evergreen instance.